Reversible Actuation and Property Recovery of Amphiphilic Triblock Copolymer Fibers Produced by Wet-Spinning
Open Access
- Author:
- Matuszewski, Kelly
- Area of Honors:
- Materials Science and Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Robert John Hickey, III, Thesis Supervisor
Robert Allen Kimel, Thesis Honors Advisor - Keywords:
- block copolymer
materials science
actuator
soft robotics
hydrogel - Abstract:
- The development of small-scale actuators for applications in soft robotics and artificial muscles is a growing field in the space of materials science research. Polymeric materials have potential in the space of soft actuators because of their ability to provide small-scale stimuli responsiveness, compliance, and light weight. The work presented in this thesis explores how the triblock copolymer system of polystyrene-b-poly(ethylene oxide)-b-polystyrene (SOS) can be utilized as a small scale fiber actuator which is responsive to heat and moisture stimuli. The creation of fiber actuators is a two-step process in which physically crosslinked hydrogel fibers are first made and then strained to form highly aligned PEO crystalline domains. Triblock copolymer self-assembly and the formation of physical crosslinks provides mechanical stability to the hydrogel. Gel fibers are produced using wet-spinning, which utilizes solvent-non-solvent rapid injection of dissolved polymer solution into water. Wet-spinning introduces uniform processing and controlled injection rate compared to previous methods of hand injection. Once hydrogel fibers were made, they were strained to 5x their original length to induce crystallization of the poly(ethylene oxide) block along the length of the fiber. These crystals can be melted at temperatures above 66 °C or when exposed to water, producing an actuation response. In this work, the actuation behavior in response to these stimuli and the subsequent actuation properties were measured. Results in this study demonstrate that the actuation length change, actuation velocity, and energy density are reversible processes. The properties are fully recoverable for at least two cycles once the fiber has been restrained. This study also investigates the dependence of actuation properties on needle gauge, strain rate, and actuation stimulus. This thesis aims to establish a fundamental understanding regarding the use of triblock copolymer fibers as actuators in the growing field of soft robotics.